Shuttle Discovery Launch Doesn’t Resolve All Problems
Flawless Flight Follows Safety Warnings
Top NASA leaders won their gamble that safety concerns about the Space Shuttle Discovery were wrong, but the picture-perfect Fourth of July launch to the heavens doesn’t mean that there are no concerns for future shuttle launches.
Soaring above warnings by two top NASA officials who asserted it wasn’t safe to fly, the Discovery mission (STS-121) to the International Space Station (ISS) was as close to perfection as any recent space mission. Launches “don’t get much better than this,” said an elated NASA Administrator Michael Griffin.
The boffo Discovery performance raises the curtain on a return to steady, repeated shuttle launches, including the Space Shuttle Atlantis launch Aug. 28, according to Griffin and Mike Leinbach, space shuttle launch director. They spoke at a briefing on Independence Day, just after the flight of Discovery.
Safety warnings asserted that, during launch and ascent, chunks of insulating foam might rip loose from the external fuel tank and hit the shuttle orbiter craft, damaging it gravely. But no foam-caused damage occurred, and the orbiter arrived at the International Space Station (ISS) in clean shape.
The positive points here:
- Almost all the pieces of foam that did break loose from the external tank were so small they were of negligible concern.
- And foam losses occurred so late in the ascent that even larger pieces would have been unlikely to damage the orbiter (because the atmosphere is so thin there, and it is the atmosphere that can accelerate pieces of foam to lethal velocities).
While the sterling Discovery performance shows a marked progress in reducing foam insulation loss, there is no guarantee that the problem is solved and never again will present a concern, or that other safety concerns won’t arise, NASA officials said.
Before Atlantis flies, “we still have a lot of work [to perform before] the upcoming mission,” said Bill Gerstenmaier, NASA
“Just having one good flight under your belt doesn’t change that direction” to attempt to discover and eliminate safety hazards, Wayne Hale, space shuttle program manager, said in a later briefing.
While the Discovery flight may have shown that changes (such as removing the protuberance air load, or PAL, ramp) seem to have lessened foam loss, it isn’t guaranteed that all flights will go so smoothly.
For example, even on this Discovery flight, one unexpected pre-flight development came when a crack was discovered in some foam, apparently caused by rain from a passing storm turning to ice and splitting the foam. Engineers determined that it nonetheless was safe to fly, and they were proved correct.
“This is a great improvement from where we were,” Hale said.
However, Griffin didn’t make use of an opportunity, presented by a news media question, to assail Bryan O’Connor, NASA chief safety and mission assurance officer, and Chris Scolese, chief engineer, who recommended against letting Discovery fly.
O’Connor and Scolese wanted to delay the STS-121 mission until further safety improvements could be made to ensure that insulating foam couldn’t tear loose from the shuttle external fuel tank and hit the orbiter vehicle.
In 2003, the leading edge of the wing on Space Shuttle Columbia was hit by a piece of foam that punched a hole in the heat shield. Later, upon reentry Feb. 1, 2003, blistering hot gases entered the wing and caused structural failure, leading to the loss of the orbiter vehicle and crew of seven.
Griffin recently rejected the “no-go” recommendations from O’Connor and Scolese, saying changes to reduce the amount of insulating foam on the Discovery external fuel tank meant odds favored a safe flight. Further, Griffin said, there would be no chance that a crew unknowingly would attempt to fly a damaged Discovery through re-entry back to a landing. Rather, he said, the crew members could use the ISS as a life raft until another spaceship could provide them with a safe ride home.
While some saw this as a roll of the dice that Griffin, and NASA, won, he sees it instead as a rational, careful assessment of risks he conceded do exist, then making a sound decision based on known and unknown variables.
Asked shortly after the launch whether he felt vindicated by the success of the Discovery ascent to orbit, Griffin demurred.
“The decision that we made was obvious” when it finally was reached, though reaching that decision “took us a long time,” he said. “The decision really made itself.”
If anything was vindicated, he said, it was the scientific process of evaluating the foam liberation problem and its threat, and then assessing means of lessening that risk.
In approaching the Atlantis launch Aug. 28, it will be in the afternoon, just as the Discovery liftoff, according to Leinbach. “It will be a [sun] lit launch,” he said, so that any foam loss can be seen and recorded on videos.
Multiple cameras, including one on the external tank during the Discovery launch, provided clear pictures showing no losses of huge foam chunks, while also picking up losses of small “popcorn” foam pieces.
The video will help NASA examine just how well its safety fixes worked, including removal of the PAL ramp, and work on the ice frost ramps and heater cables, according to John Shannon, deputy shuttle program manager.
Assessing changes to the tank after viewing the videos for more than a day after the launch, NASA leaders “feel really good about it,” Shannon said.
Robotic arms also snaked out to provide a further meticulous examination of critical areas such as the nose and wing leading edges on Discovery, and again found no major damage. Some loose shims or fabric-like material protruded alongside a few heat tiles, but that was it.
Further, as Discovery neared the ISS, it passed before cameras on the space station that checked further for possible damage.
Several NASA leaders emphasized that there are many potential problems that can arise in a shuttle flight aside from foam loss, and all of these problems must be addressed.
More generally, Hale observed, space travel is and will be “an inherently risky business.”